blk-cgroup: rwstat: fix kernel-doc warnings in header file

Correct the function parameters to eliminate kernel-doc warnings:

blk-cgroup-rwstat.h:63: warning: Function parameter or struct member 'opf' not described in 'blkg_rwstat_add'
blk-cgroup-rwstat.h:63: warning: Excess function parameter 'op' description in 'blkg_rwstat_add'
blk-cgroup-rwstat.h:91: warning: Function parameter or struct member 'result' not described in 'blkg_rwstat_read'

Signed-off-by: Randy Dunlap <[e-mail]>
Cc: Tejun Heo <[e-mail]>
Cc: Josef Bacik <[e-mail]>
Cc: Jens Axboe <[e-mail]>
Cc: [e-mail]
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Jens Axboe <[e-mail]>

block/blk-cgroup-rwstat.h

···
 /**
  * blkg_rwstat_add - add a value to a blkg_rwstat
  * @rwstat: target blkg_rwstat
- * @op: REQ_OP and flags
+ * @opf: REQ_OP and flags
  * @val: value to add
  *
  * Add @val to @rwstat.  The counters are chosen according to @rw.  The
···
 /**
  * blkg_rwstat_read - read the current values of a blkg_rwstat
  * @rwstat: blkg_rwstat to read
+ * @result: where to put the current values
  *
- * Read the current snapshot of @rwstat and return it in the aux counts.
+ * Read the current snapshot of @rwstat and return it in the @result counts.
  */
 static inline void blkg_rwstat_read(struct blkg_rwstat *rwstat,
 		struct blkg_rwstat_sample *result)